Randy Smith

OK, I need some help here.
I have installed a Hitec 555 receiver into my plane with some HS-205's and an HS-80 on the throttle. I have a Futaba 8UAP transmitter.

Twice now, after the model has sat turned off for a few days, when I turn the power on (Tx first, then receiver), the servos move to the extreme ends of travel and then proceed to strip out the gears on the HS-80 servo. This is very frustrating.

The second time this happened I turned the power off and tried the power up procedure again and again. The movement of the servos to their extreme ends repeated itself for about four or five power up cycles. Then it mysteriously resumed normal behavior.

It is a brand new switch, fresh battery, etc, etc. Has anyone else had this trouble. I'm running out of gear sets......


Randy S.

Glen Merritt

Very freaky.

Quick questions:

Have you flown this plane with this set-up?
Do you have a Hitec crystal in the 555 Rx?
What is the Rx. battery voltage (number of cells)?


Glen Merritt
Hitec USA

Randy Smith

Hi Glen,
No, I have not flown the model yet. I'm just setting it up on the bench. Yes, it has a Hitec crystal in the receiver.

Battery voltage is a five cell (6 volt) nicad pack. Also had the same thing happen using a 7.2v lithium. Is this voltage too high for the 555 receiver ? I have several other models which I have used a 5 cell nicad pack for years with no problems at all. First time for the lithium however.

Randy

Glen Merritt

Lithium cells are not to be used as an Rx power source unless a regulator is used. You may have "popped" something in the Rx. Did the effect you describe occur before the Lithium cells were used or after?


I have to ask, are you sure you are in PPM mode and not PCM?

Sincerely,

Glen

Randy Smith

Hi Glen,
' Sorry for the long delay in response. I have been off-line for a while.

I checked PPM vs PCM and I am set for PPM.
The first time the problem occured (with this set up) was with the Lithium pack. However, I have run the 555 and other receivers on the Lithium pack without a regulator and there has been no problem.

It seems to be very intermittent. Somedays it will do it and others it won't . I never know when it will take out my gears.

Randy

Glen Merritt

Randy,

Can't really say you "have not had any problems" because you ARE experiencing a rather strange and unusual problem. The one thing you have done is use lithium cells without a regulator to run an Rx. I must repeat that is not advised by any Rx. manufacturer I am aware of. The input voltage simply exceeds the design parameters and that is just asking for trouble.

Two suggestions;

I would suggest the 555 Rx. be looked at by a service facility to see if there is a problem with it.

Another option is to try a 4.8 cell pack to see if the problem goes away. There is no rational reason why it would matter but it is something to try.

Glen Merritt
Hitec USA

Zoomer02

I had this same thing happen to me. I purchased a micro flight pack. I built the wing with the servos for the ailerons inside and did not make access panels for the first time since I never have had to get back at them before. The battery that came with the kit had the leads reversed. I did not notice this until later. When I plugged it all in for the first time I noticed that both of the servos were stripped. I have now cut open the wing and I am replacing the HS-81 servo gears with the metal gearset so that hopefully this will not happen in the future. I never stripped a servo without crashing a plane and this one is not even finished being built!